This study is aimed to investigate the effects of relationship emotional contagion on Electronic Word of Mouth (E-WOM Quality, E-WOM Quantity, Sender's Experience), by focusing on the Mobile Phone Brand Customers of Social Network Sites in Egypt. According to the literature review, an analytical model is developed as guidance to test the relationship between the research variables. The Sample Size is 384, and the valid questionnaires are 312, an estimated 90% Of the total Sample Size. The findings show that there is a significant, positive, and direct effect of Emotional Contagion on E-WOM Quality (Cognitive, Emotional, Behavioral). The study also finds that there are significant differences between customer's opinions according to their demographic characteristics (gender, age, social status, educational level, monthly income) regarding emotional contagion, and E-WOM.